1. Field of the Invention
The present invention relates to an image display apparatus for projecting and displaying a wide-image-angle, high-fine image on the retina.
2. Description of the Related Art
In a conventional apparatus of this type, an image display portion and an observer's retina conjugate with each other. An image produced by a display element of an image display unit is transmitted through an image transmission medium and then focused on the retina by the optical system of the eye.
There is known a conventional, simple method for producing a wide-image-angle, realistic image by using the above apparatus. In this method, an image on the display element is enlarged and displayed on the retina (Prior Art 1).
Production of image on the retina is based on the refraction of the eye. Thus, in the conventional apparatus, if a person with abnormal refraction performs observation, he/she must put on glasses, contact lenses or the like in order to add a function for visibility adjustment to the optical system and thereby to correct the abnormal refraction.
According to another method for correction, a high-fine image free from diffraction or aberration can be reproduced on the retina by bypassing the optical system of the observer's eye.
Jap. Pat. Appln. KOKOKU Publication No. 3-51167, for example, dislcose methods for reproducing an image on the retina by bypassing the optical system of the eye.
In these methods, by producing two point light sources which can interfers with the pupil face of the eye, a Young interference fringe is formed on the retina.
At this time, the pupil eye and retina have a relationship of Fourier inverse transform. The spatial frequency of interference fringe is set at a distance between the point light source, and the direction in which the fringe extends is perpendicular to the direction of arrangement of point light sources formed on the pupil face.
Since the optical system of the eye is not concerned with the formation of the interference fringe, the image can be formed on the retina with a high contrast, even when an interference fringe of high spatial frequency has been produced.
Another method of reproducing an image on the retina by bypassing the optical system of the eye is disclosed, for example, in Jap. Pat. Appln. KOKAI No. 2-136818 (Prior Art 2).
In this method, the image produced by the display element is directly focused on the observer's retina via an eye lens situated just in behind of the display element.
However, in the apparatus of Prior Art 1, since the pixels of the display element are enlarged along with the image, it is possible that each pixel is sensed or a band is limited, resulting in degradation in image quality. Specifically, the spatial resolution characteristics of the entire optical system are restricted by the spatial resolution characteristics of the display element.
In the apparatus of Prior Art 2, the image can be formed on the retina, without depending on the optical characteristics of the eye. However, like Prior Art 1, if the image of the display element is enlarged to obtain the wide-image-angle retinal image, the pixels of the image of the display element are also enlarged, and each pixel is sensed. Thus, the spatial resolution characteristics of the entire optical system are restricted by the spatial resolution characteristics of the display element.